The present invention relates to a chuck assembly for holding a workpiece for processing, and more particularly to such a chuck assembly which uses counterweights to balance its rotation, and a springy jaw holder to hold jaws and a T-block for holding down the workpiece.
FIG. 1 illustrates a chuck assembly for use in a cutting metalworking machine to hold the workpiece for processing. The chuck assembly is coupled to the rotary driving member 60 of the air cylinder of the cutting metal-working machine, comprised of a push block 61, a jaw holder 62, a coupling tube 621, and jaws 63. The push block 61 is mounted in the jaw holder 62. The coupling tube 621 is mounted within the push block 61 and coupled to the rotary driving member 60. The jaws 63 are equiangularly spaced at one side of the jaw holder 62. The jaw holder 62 has an axle hole 622 at the center, and equiangularly spaced radial grooves 620 of crossed cross section. The jaws 63 each comprise a slide 630 moved in one radial groove 620 at the jaw holder 62, the slide 630 having a flange of T-shaped cross section 632 at the bottom and a groove of T-shaped cross section 631 at the top, a T-block 634 mounted in the groove of T-shaped cross section 631 at the slide 630, and a clamping block 633 mounted on the T-block 634. The push block 61 has a center through hole 612, and a plurality of T-shaped bevel grooves 611 equiangularly longitudinally spaced around the periphery. The rotary driving member 60 has a front coupling portion 601. The jaws 63 are respectively mounted in the radial grooves 620 at the jaw holder 62. The flange of T-shaped cross section 632 of the slide 630 of each jaw 63 is respectively engaged into the bevel T-shaped bevel grooves 611 at the push block 61. When the rotary driving member 60 is moved forwards, the push block 61 is moved forwards with the rotary driving member 60, thereby causing the jaws 63 to be radially pushed outwards, and therefore the workpiece is released. On the contrary, when the rotary driving member 60 is moved backwards, the push block 61 is moved backwards with the rotary driving member 60, and the jaws 63 are respectively moved along the bevel T-shaped bevel grooves 611 toward the center of the jaw holder 62 to hold down the workpiece. Therefore, moving the rotary driving member 60 axially backwards/forwards causes the jaws 63 to hold down/release the workpiece. However, this structure of chuck assembly is still not satisfactory in function. The drawbacks of this structure of chuck assembly are numerous as outlined hereinafter:
1. Because the chuck assembly is comprised of a number of parts including push block, jaw holder, coupling tube, and jaws, the manufacturing cost is high, and the assembly process is complicated. During the assembly process, it is difficult to position the parts of the jaws relative to one another. PA0 2. The arrangement between the T-block and the clamping block, the slides and the radial grooves, the flange of T-shaped cross section and the groove of T-shaped cross section at the slide, the front coupling portion of the rotary driving member and the push block, must be precisely matched. PA0 3. Frequently reciprocating the rotary driving member, the push block and the slides to release/hold down the workpiece causes the related parts to rub against one another, and frequently rubbing the parts against one another causes the related parts to wear quickly. PA0 4. The chuck assembly has no means to neutralize centrifugal force during its operation, which centrifugal force hinders the chuck assembly from a high-speed rotary motion. PA0 5. Because the chuck assembly has no means to neutralize centrifugal force, it is not suitable for holding down a workpiece of thin wall thickness.